Inclusion Criteria: (1) age between 50 and 80 years; (2) a post-bronchodilator forced expiratory volume in one second (FEV1) < 80% of the predicted value and a FEV1/ forced vital capacity (CVF) ratio < 0,7; (3) stable respiratory/clinical condition without changes in medication and symptoms (dyspnea, volume or color of sputum) for at least 4 weeks before admission to the study; and (4) receiving regular treatment with inhaled bronchodilators and steroids.